Firefighting and other forms of field work demand a high level of fitness
to safely perform arduous day-long work in difficult environmental conditions,
including steep terrain, extreme temperatures, altitude, and smoke, and
to meet unforeseen emergencies. When prolonged hard work is involved,
fitness is the most important factor in work capacity.

Work capacity is a composite of fitness,
acclimatization, nutrition, skill, experience, motivation, and intelligence.
Fitness is the most important factor. Fitness has two components, aerobic
and muscular.

Aerobic fitness is a measure of your
ability to supply working muscles with the oxygen they need to perform
vigorous day-long work. When you can deliver and use oxygen efficiently,
you can do more work without undue fatigue.

Muscular fitness includes strength,
muscle endurance, and flexibility. Strong workers can lift and carry heavy
loads with less fatigue or risk of injury. Muscular endurance enables
you to continue working at otherwise fatiguing tasks. And flexibility
means a better range of motion that lowers the risk of injury.

Fitness is the foundation of work capacity. That's why resource agencies
stress its importance,
and why you should report to the job fit, work-hardened, and ready to
take on tough field assignments.

Gaining fitness is a gradual process that can take 2 to 3 months for
substantial improvements. Working yourself into shape on the job is not
an option. Some
jobs, like firefighting, require that you pass a job-related work capacity
test to ensure the capacity to perform arduous work. In field work, particularly
firefighting, fitness is a matter of safety both for you and your crewmembers.